Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United StatesDepartment of Energy s National Nuclear Security Administration under contract DE-AC04-94AL85000.
Status of Z-Pinch ICF ResearchStatus of Z-Pinch ICF Research
Fusion Power Associates Meeting
September 27, 2006
Keith Matzen
Sandia National Laboratories
Non-cryogenicCryogenic
Double shellFast ignitionHot spot
ignition
Vacuum
hohlraum
Dynamic
hohlraum
Driver ICF Target
X-ray
drive
BeCu-Foam
Au/Cu
DT
Au
2
The goal of the Pulsed Power ICF program
is to validate a High Yield target design
Eff
icie
ncy
Risk
Double-ended
hohlraum
Dynamic
hohlraum
Advanced concepts
(Fast Ignitor)
We are presently studying 3 High Yield target concepts
3
Pulsed-power provides
compact, efficient, power amplification
0
50
100
150
200
0 0.5 1 1.5
Pow
er (
TW)
Z
Time(µs)
x ray output~1.6 MJ~200 TW
Marx
11.4 MJ
water
vacuum
Electrical to x-ray energy
Conversion efficiency ~ 15%
Efficiency Low Cost
17 m radius
4
Indirect drive ICF: a spherical capsule is imploded by
z-pinch-produced x-rays contained in a hohlraum
JxB
Target heating Compression Ignition Burn
5
The double-ended hohlraum high yield concept separates
capsule, hohlraum, and z-pinch physics issues
z-pinch energetics
pulse shaping
hohlraum coupling
radiation symmetry
hohlraum energetics
capsule physics
pinch simultaneitypinch balance
6
A focused effort began in Sept 2005 to create a modern
reference design for the double-ended hohlraum (DEH)
Integrated 2D simulations with capsule implosion/ignition/burn were
not achieved in the 1999 study, mainly due to symmetry issues
Key results of initial scoping study:
• 400 MJ yield capsule
• 16 MJ total x-ray energy output from 2 pinches
• 2 x 62 MA currents required with 100 ns rise time
• Pulse shaping via multi-shell z-pinch load design
• Spoke x-ray transmission of > 60% required
• Pinch power balance of 7% required
25 mm
~35 m
m
7
• Consistency of z-pinch and hohlraum
energetics documented at ± 20% level in flux
• Spoke transmission measured to be > 70%
2D Lasnex simulations of hohlraum energetics and
symmetry have been validated in DEH experiments on Z
4.7-mm capsules
2.15-mm
capsules
LASNEXLASNEX
Backlit capsules confirm equator/pole
symmetry tuning vs. lengthBacklit capsule trajectories
confirm hohlraum coupling
M. Cuneo et al., Phys. Plasmas 2001
G. Bennett et al., Phys. Plasmas 2003
R. Vesey et al., Phys. Plasmas 2003
R. Vesey et al., proc. IFSA 2005
8
Baseline DEH capsule uses a 0.2% Cu-doped Be
ablator, absorbing 1.2 MJ of x-rays, yielding 520 MJ
DT gas 2180 µm (0.3 mg/cm3)
solid DT 280 µm
Be (0.2% Cu) 190 µm
DEH capsule design
Outer radius = 2.65 mm
3536Hot spot convergence ratio
29%33%Fuel KE margin
3519Inflight aspect ratio
60160Drive pressure (MB)
0.070.06Fuel fraction at >1.5 if
0.730.93if
26.037.0Implosion velocity (cm/µs)
3.11.9Peak r (g/cm2)
52013Yield (MJ)
1.210.14Absorbed energy (MJ)
28080DT fuel thickness (µm)
190160Ablator thickness (µm)
DEHNIF GDBECapsule
9
Although not optimized, the 220 eV DEH capsule
robustness compares well with the NIF GDBe capsule
0.00
0.20
0.40
0.60
0.80
1.00
0.0 5.0 10.0 15.0 20.0
Surface perturbation tolerancedue to RT instability (mode 12)
Yield
over
Clean
Yield
300 eV
1.0 mm
D1GDBE
220 eV
2.65mm
DEH
Work is underway to define a more robust 220 eV capsule:
• radially-dependent level of Cu dopant in Be shell
• optimization of capsule AND pulse shape
initial perturbation (a.u.)
86
101 120
146
215
230
Pulse shape tolerances(>90% full yield)
Foot ± 2.8 ns
Shoulder ± 1.4 ns
Peak ± 1.2 ns
10
2D Lasnex hohlraum/capsule simulations capture the
essential physics of radiation coupling and symmetry
Not included:
Self-consistent z-pinch implosion (yet)
3D asymmetry
High-mode RT instability in capsule
Included:
Moving x-ray source pinch model r(t), P(t)
Radiation transport
Hohlraum wall radiation-hydrodynamics
Magnetic tamping of primary hohlraum
Spoke transmission as radiation b.c.
Capsule implosion and asymmetry
Capsule ignition and burn
primary
hohlraum
secondary
hohlraum
primary
hohlraum
11
Low-mode symmetry control in the “baseline” hohlraum
configuration is not adequate for ignition capsules
Similar level of P4 asymmetry measured in foot-like Z experiments
z
r
Fuel density contours at
peak convergence
Yield = 0.040 MJ
max = 310 g/cc
P2 = -0.2 %
P4 = -3.3 %
P6 = +0.0 %
P8 = +0.2 %
P2 = -1.0 %
P4 = -0.3 %
P6 = -0.4 %
P8 = 0.0 %
Ablation pressure asymmetry
Foot Main
All walls Au50Gd50
P4
P2Tr
12
Secondary entrance foams and P4 shields give low
time-dependent P2, P4, P6, and P8 asymmetry
Foot pulse End foot Peak pinchInitial
9o shield
P2 = 0.0 %
P4 = +0.2 %
P6 = +0.1 %
P8 = +0.1 %
P2 = -0.3 %
P4 = -0.8 %
P6 = +0.1 %
P8 = +0.4 %
P4 shield :
100 mg/cc CH2 (3% Ge)
Sec. entrance foam :
5 mg/cc CH2
13
Secondary entrance foams and P4 shields
have resulted in highly symmetric capsule
implosions that yield nearly 500 MJ
Ablation pressure asymmetry
P4 shield: 4.4o, 200 mg/cc
Fuel density contours
near ignition
Yield = 470 MJr = 2.7 g/cm2
max = 580 g/cc
z
r
Initial P4 control set by shield angular range, duration set by density ( x)
Resolution convergence studies are underway
P4
P2
Tr
14
Hohlraum / capsule simulation summary
2 main goals of hohlraum/capsule simulations have been met:
Demonstrated ignition and burn in best available 2D models
Developed strategy to control time-dependent symmetry
Identified a new technique for mode-selective symmetry control
with small angular range shields
P4 is tunable with negligible effect on P6 and P8 at capsule
Solutions exist with 2 shields per side that should tune P4 with
exactly zero effect on P2, P6, and P8 (to be tested)
Work is in progress (Herrmann) to define more robust capsule designs
Concept separates z-pinch from capsule – design z-pinch load in parallel
Each pinch should provide 9 MJ total, with 0.5 MJ foot pulse 20-25 ns prior to peak
Design work is in process with Alegra (2D & 3D) and Lasnex (1D & 2D)…
15
Recent z-pinch simulations produced an x-ray
pulse shape capable of igniting a capsule
Z-pinch x-ray power history
2D calculation
Ideal pulse
(used in baseline capsule design)
void
R=1.2 cm
81 mg
Alegra simulation
Nested Be-Be-CH2 shells
Z voltage x 5.3
Load design has evolved to provide good foot – shoulder – peak timing
The total x-ray energy output is more than adequate at ~10 MJ
16
Be liners
collide
CH2
Radiation pulse features are produced by shock
heating when z-pinch components collide
1st strike
Be-CH2
CH2
Be
tailored shock
front
begin shock
stagnation
on axis
stagnationon-axis
stagnation
radiative
cooling phase
Z-Pinch density (r,z)
170 TW
foot
290 TW
shoulder
1570 TW
main
Amplitude of radiation pulse feature produced by shock event depends
on kinetic energy flux of impactor and opacity (optical depth).
17
Pulse compression with single arrays
+46%
1998
2003 2002
2.7
ns
Reproducible, controllable shapes with nested arrays
2002-2004
We have made significant progress in power scaling,
reproducibility, and pulse shaping of wire array z-pinches
1
2 3
1
2 3
60
80
100
120
140
160
180
200
10 12 14 16 18 20
Pea
k x-
ray
Po
wer
P (
TW
)
Peak Load Current (MA)
P I1.25 ± 0.18
P I1.82 ± 0.15
Current scaling of single arrays
2003-2004
2002-2003
Pulse compression with nested arrays
+58%2005
210 TW
2.4 ns
130 TW
18
20 µm resolution radiography provides new
opportunities for capsule implosion studies
• Embedded-glass capsule
• 6.151 keV backlighter
• ZBL prepulse – higher flux
• Bent crystal imaging
• Imaging plate detector
• Cu aperture patches
Visible light microscopy
pits/domes
Shot Z1561 9-23-2005
3.2-mm diameter capsule
1 mm
20 µm spike / 5 pixels
Cr = 1.7
19
Progress in pulsed-power hot-spot ignition
• Integrated LASNEX hohlraum/capsule
simulations predict ignition and burn in
double-ended hohlraum configuration
• Achieved dramatic advances in our ability
to experimentally control the radiation
output of Z-pinches
• Designed power pulse shapes for high
yield capsules through z-pinch
engineering with ALEGRA-HEDP
• Record x-ray driven D-D neutron yields
with Be capsules in dynamic hohlraums
foot peak1D yield 520 MJ
2D yield 470 MJ (currently)
Radiation pulse shaping
single
wire array
nested
wire array
33 µm
Be
18 µm
CH20 atm D2
+
0.085 atm Ar
Be capsule imploded with Dynamic Hohlraum
20
We are using our experience from several science
campaigns to support the National ICF Program
• Measured Be melt pressure
• Delayed ZR shutdown to
enable diamond melt
experiments
• Fielded fill tube hydro
experiments (collaboration
with GA and LLNL)
• Performed experiments with
LANL and LLNL on Omega
• Developing NIF cryogenic
target system x-ray blast
shield
• Assessing EMP shielding for
NIF diagnostics
QMD simulations predict
shock melting at 213 GPa
Measured melt between
~200 - 250 GPa
21
Recent experiments used Z’s unique capabilities to
assess the effects of fill tubes on capsules
• Fill tube calculations are some of the most challenging calculations that have been done in
support of inertial confinement fusion ignition
• Need data to validate the computational tools used to simulate fill tubes
• Capability to do experiments on NIF-scale objects coupled with high resolution radiography
allows high utility experiments
Optical image
2 mm
Glass tubes(10-40 µm diameter)
X-ray image during implosion
(1 nanosecond snapshot)
2 mm
Fill tube
perturbations
22
Robust & Electrically Optimized:
• Intermediate Storage Capacitors
• Pulse Forming Lines
• Transmission Lines
Upgraded Power Flow –
for Higher Stresses &
Improved Diagnostic Access
Individual
Trigger Lasers
Enhanced
Diagnostics
Infrastructure
New Capacitors –
Doubles Stored
Energy
Oil
Vacuum
Water
OilWaterWater
RefurbishmentRefurbishment
ZR: Refurbishment of the Z Pulsed Power
Generator
23
Some assembly is required
24
Z Machine
70’ (21m)
• Terawatt-class Z-Beamlet
provides 1-10 keV x-ray
backlighting on Z
• Petawatt-class enhancement
allows new radiography options
(X-rays over 10-100 keV; protons)
and Fast Ignitor research on Z
• System operational in 2007 at
500 J / 500 fs with Nova gratings,
ramping up to 2 kJ in 5-10ps
The Z-Petawatt Laser System will provide
new capability for radiography and fast ignition research
Z-Beamlet
Facility
Petawatt Pulse
Compressor
Z-Beamlet HiBay
Phase C
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